Ion implantation is a standard technique for introducing conductivity-altering impurities into semiconductor wafers. A desired impurity material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the wafer. The energetic ions in the beam penetrate into the bulk of the semiconductor material and are embedded into the crystalline lattice of the semiconductor material to form a region of desired conductivity.
An ion implanter includes an ion source for converting a gas or a solid material into a well-defined ion beam. The ion beam typically is mass analyzed to eliminate undesired ion species, accelerated to a desired energy, and implanted into a target. The ion beam may be distributed over the target area by electrostatic or magnetic beam scanning, by target movement, or by a combination of beam scanning and target movement. The ion beam may be a spot beam or a ribbon beam having a long dimension and a short dimension. The long dimension usually is at least as wide as the wafer. Examples of ion implanters may be found in, for example, U.S. Pat. No. 4,922,106 issued to Berrian et al. (assigned to Varian Semiconductor Equipment Associates, Inc. of Gloucester, Mass.) and U.S. Pat. No. 5,350,926 White et al., both of which are hereby incorporated by reference.
In a plasma doping system, a semiconductor wafer is placed on a conductive platen which functions as a cathode. The desired dopant material is introduced into the chamber, and a voltage pulse is applied between the platen and an anode or the chamber walls, causing formation of a plasma having a plasma sheath in the vicinity of the wafer. The applied voltage causes ions in the plasma to cross the plasma sheath and to be implanted into the wafer. The depth of implantation is related to the voltage applied between the wafer and the anode. An example of a plasma doping system may be found in, for example, U.S. Pat. No. 4,764,394 issued to Conrad, which is hereby incorporated by reference.
In other types of plasma systems, known as plasma immersion systems, a continuous RF voltage is applied between the platen and the anode, thus producing a continuous plasma. At intervals, a voltage pulse is applied between the platen and the anode, causing ions in the plasma to be accelerated toward the wafer. An example of a plasma immersion system may be found in, for example, U.S. Pat. No. 5,354,381 issued to Sheng, which is hereby incorporated by reference. Other types of deposition methods, such as chemical vapor deposition or physical vapor deposition also may be used in wafer or workpiece processing. Other semiconductor manufacturing methods, such as lithography, may likewise be used on a wafer or workpiece.
Workpiece processing equipment used for semiconductor manufacturing typically is under vacuum in a process chamber. During typical system operation for ion implantation, undesired particles may be formed or generated. These particles may be residual beam or plasma particles, photoresist, particles from a workpiece, or other particles that exist in regions of the process chamber and that may settle on a surface, base, or floor within a process chamber. Particles may, for example, break off a film formed on a surface within an analyzer magnet and settle to the base of that analyzer magnet process chamber.
During periodic maintenance, various process chambers used for semiconductor manufacturing may be open to the atmosphere or a process gas. The venting of such process chambers often leads to turbulent fluids being introduced to a process chamber. Particles that have settled on the floor, base, or other surfaces in a process chamber may then be disturbed or agitated and redistributed throughout the process chamber's interior. Due to additional cleaning required to remove these particles, re-qualifying the process chamber becomes more difficult and time consuming.
Prior particle isolation technology includes, for example, charged process chamber walls or charged plates or electrodes. This technology also may include mechanical means such as channels or fixed louvers. This technology also may include adhesive material or particle capturing material. However, these types of particle isolation technology may release trapped particles when a process chamber is vented and the particles are disturbed by turbulent fluids entering the process chamber. This may distribute the particles throughout the process chamber and may require additional cleaning to re-qualify the process chamber. These types of particle isolation technology also lack particle isolation devices that may be quickly removed.
Accordingly, there is a need in the art for a new and improved apparatus and method of particle isolation within semiconductor manufacturing process chambers.